From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mark Dilger <mark.dilger@enterprisedb.com>
cc: PostgreSQL-development <pgsql-hackers@postgresql.org>
Subject: Re: Assert triggered during RE_compile_and_cache
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Comments: In-reply-to Tom Lane <tgl@sss.pgh.pa.us>
	message dated "Sat, 07 Aug 2021 21:03:26 -0400"
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Date: Sun, 08 Aug 2021 12:31:53 -0400
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I wrote:
> While this is sufficient to make the problem go away, I'm
> inclined to apply both changesets.  Even if it accidentally
> works right now to have later backrefs consult the outer s/s2
> state pair rather than the original pair, that seems far too
> convoluted and bug-prone.  The outer states should be strictly
> the concern of the iteration setup logic in the outer invocation
> of parseqatom.

> (I'm sort of wondering now whether the outer s/s2 states are
> even really necessary anymore ... maybe Spencer put those in
> as a way of preventing some prehistoric version of this bug.
> But I'm not excited about messing with that right now.)

I realized that the earlier patch is actually a bad idea, because
it breaks the possibility of updating the subre to mark it as
being referenced by a later backref, as the REG_NOSUB patch needs
to do.  However, on closer study, the outer s/s2 states being
added by the "prepare a general-purpose state skeleton" stanza
really are duplicative of the ones we already made for a
parenthesized atom, so we can just get rid of them.  Done that
way.

			regards, tom lane